Post-CMP removal of surface contaminants from silicon wafer

ABSTRACT

A method of removing contaminants from a silicon wafer after chemical-mechanical polishing (CMP). After a copper chemical-mechanical polishing and a subsequent barrier chemical-mechanical polishing operation, an aqueous solution of ozone in de-ionized water is applied to clean the silicon wafer so that contaminants on the wafer are removed. Alternatively, an ozone/de-ionized water buffer-polishing process is conducted after copper and barrier CMP and then the wafer is cleaned using a chemical solution or de-ionized water. Alternatively, an ozone/de-ionized water buffer-polishing process is conducted after both copper-CMP and barrier-CMP and then the wafer is cleaned using a chemical solution or de-ionized water.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of Taiwanapplication serial no. 90109738, filed on Apr. 24, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of Invention

[0003] The present invention relates to a planarization process insemiconductor manufacture. More particularly, the present inventionrelates to a post chemical-mechanical polishing (CMP) cleaning of asilicon wafer.

[0004] 2. Description of Related Art

[0005] In the manufacturing of deep submicron semiconductors, a copperdamascene process to form a conductive line in a low dielectric constant(low-k) inter-metal dielectric layer is an effective method of loweringresistor-capacitor (RC) delay and resisting electromigration resistance.In a damascene process, one important step is copper chemical-mechanicalpolishing (Cu-CMP) for the removal of excess copper above a dielectricsurface.

[0006] Chemical-mechanical polishing is an operation that utilizes themechanical grinding action of a polishing wheel and the chemical actionof a suitable chemical agent to planarize the undulating surface profileof a silicon wafer. Principle components of a chemical-mechanicalpolisher include a polishing table for grinding the silicon wafer and ahandle for grasping the back side of the silicon wafer. To carry out achemical-mechanical polishing, the back side of the wafer is grasped bythe handle while the front side of the wafer is pushed against apolishing pad on the rotating polishing table. Chemical agents necessaryto assist the polishing such as slurry is delivered along a pipelinesystem to the polishing pad. Utilizing the abrading action of thepolishing pad and the chemical action of the slurry, the front surfaceof the wafer is planarized.

[0007] However, during a chemical-mechanical polishing operation,contaminants that originate from the slurry or abrasive particles in thepolishing pad may settle on the wafer surface after polishing. In thepolishing of a copper/low dielectric constant material on a siliconwafer, by-products or carbon-rich particles may also settle onto thewafer surface after polishing.

[0008] In a copper chemical-mechanical polishing operation, a barrierlayer or an etching stop layer on the low dielectric constant materiallayer are often used as a stop layer in a barrier chemical-mechanicalpolishing (barrier-CMP) operation. However, the process frequently leadsto a dishing of the surface of copper conductive lines and an exposureof the low dielectric constant material near the edges of the copperlines. Consequently, a portion of the low dielectric constant materialis likely to be polished away, generating large quantities ofcarbon-rich particles on the wafer surface. In addition, because thecarbon atoms within most types of neutral-to-acidic slurry have apotential opposite to that of a copper surface, the carbon-richparticles are likely to attach to the copper surface, producing surfacedefects.

[0009] To remove the contaminants on a silicon wafer, a cleaning step isoften added after chemical-mechanical polishing. At present, mostintegrated circuit manufacturers opt for cleaning the wafer with anaqueous chemical solution or de-ionized (DI) water in combination withsome form of brushing, jetting or ultrasound. De-ionized water removesthe contaminants by the application of external forces. Aqueous chemicalsolution removes the contaminants by attacking the wafer surface orreacting with the contaminants before removing the dislodgedcontaminants from the wafer.

[0010] However, cleaning a wafer with de-ionized water cannot remove allsurface contaminants. On the other hand, using an aqueous chemicalsolution to remove contaminants may damage the wafer surface. Moreover,some of the contaminants may be chemically inert to the chemicalingredients in the aqueous solution. For example, carbon-rich particlesor chemical reaction by-products attached to the wafer may not be easilyremoved by the chemicals in the aqueous solution.

[0011] Methods related to the removal of contaminants on a silicon waferafter chemical-mechanical polishing can be found in various articles.For example, N. Miyashita et al. have written an article titled, “A newpost-CMP cleaning method for trench isolation process in CMP” (MICconference, 1996). The proposed method involves using an activatedinterfacial reagent to carry out chemical-mechanical polishing so thatthe surface of the polysilicon film remains hydrophilic afterchemical-mechanical polishing and waste particles are removed in-situ.

[0012] All the aforementioned conventional cleaning methods areinefficient in removing most contaminants from a silicon wafer andmaintaining post CMP wafer surface properties. Hence, semiconductormanufacturers are still looking for an effective and economic post-CMPcleaning that can effectively remove contaminants from a wafer surfacewith as few changes in surface properties as possible.

SUMMARY OF THE INVENTION

[0013] Accordingly, one object of the present invention is to provide amethod of completely removing contaminants from a silicon wafer after achemical-mechanical polishing. The method includes applying an aqueoussolution of ozone. Ozone molecules have an exceptional atomic cleansingeffect and minimal by-product generation. In addition, the use of anaqueous ozone solution produces less environmentally toxic exhaust thanconventional cleaning methods and ozone molecules have the capacity ofneutralizing charged contaminants. Ultimately, surface contaminants areefficiently removed leading to the production of fewer surface defectsand the use of fewer chemical reagents.

[0014] To achieve these and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, theinvention provides a method of removing contaminants from a siliconwafer after chemical-mechanical polishing (CMP). After a copperchemical-mechanical polishing and a subsequent barrierchemical-mechanical polishing operation, an aqueous solution of ozone inde-ionized water is applied to clean the silicon wafer so thatcontaminants on the wafer are removed. Alternatively, anozone/de-ionized water buffer-polishing process is conducted aftercopper and barrier CMP and then the wafer is cleaned using a chemicalsolution or de-ionized water. Alternatively, an ozone/de-ionized waterbuffer-polishing process is conducted after both copper-CMP andbarrier-CMP and then the wafer is cleaned using a chemical solution orde-ionized water.

[0015] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary, andare intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings, FIGS. 1A through 1D areschematic cross-sectional views showing the progression of steps forforming a damascene structure according to one preferred embodiment ofthis invention;

[0017]FIG. 2 is a flow chart showing the steps for removing contaminantsfrom a silicon wafer after chemical-mechanical polishing according to afirst preferred embodiment of this invention;

[0018]FIG. 3 is a flow chart showing the steps for removing contaminantsfrom a silicon wafer after chemical-mechanical polishing according to asecond preferred embodiment of this invention; and

[0019]FIG. 4 is a flow chart showing the steps for removing contaminantsfrom a silicon wafer after chemical-mechanical polishing according to athird preferred embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

[0021] The method of this invention is suitable for removingcontaminants from a silicon wafer both during and after achemical-mechanical polishing. A damascene process is used in thefollowing example for illustrative purpose only. Hence, the illustrationshould not be regarded as a restriction to the application of thisinvention.

[0022]FIGS. 1A through 1D are schematic cross-sectional views showingthe progression of steps for forming a damascene structure according toone preferred embodiment of this invention.

[0023] As shown in FIG. 1A, a substrate 100 (the diagram is simplifiedby not showing devices on the substrate 100) is provided. A dielectriclayer 102 is formed over the substrate 100. The dielectric layer 102 canbe a low dielectric constant material layer such as a vapor-phasedeposition polymer (VPDP) layer, a spin-on polymer (SOP) layer or aspin-on-glass (SOG) layer. The dielectric constant material layer mayinclude ingredients such as fluoride-containing organic polymer,fluorinated hydrocarbon, fluorinated poly-(arylene-ether) (FLARE),non-fluorinated aromatic polymer or hydrogen silsesquioxane. Thedielectric layer 102 is formed, for example, by spin-coating or chemicalvapor deposition.

[0024] Using photolithographic and etching techniques, the dielectriclayer 102 is patterned to form an opening 104. The opening 104 can be,for example, a damascene opening for forming a dual damascene structure,a trench opening for forming a conductive line, a via opening forforming a plug or an opening for forming a damascene structure (a dualdamascene opening is shown in FIG. 1A).

[0025] As shown in FIG. 1B, an etching stop layer 106 conformal to theinterior surfaces of the opening 104 and covering the dielectric layer102 is formed. The etching stop layer 106 can be a silicon nitride (SiN)layer, a carbon silicide (SiC) layer, or a silicon oxide (SiO_(x)) layerfor example. Thereafter, using photolithographic and etching techniques,the etching stop layer 106 within the opening 104 is removed.

[0026] A conformal barrier layer 108 is formed over the exposedsubstrate 100, the dielectric layer 102 and the etching stop layer 106.The barrier layer can be a tantalum nitride (TaN) or silicon nitride(SiN) layer, for example.

[0027] Metallic material is next deposited over the barrier layer 108and fills the opening 104 to form a metallic layer 110. The metalliclayer 110 can be a copper layer, a tungsten layer or an aluminum layerformed, for example, by physical vapor deposition (PVD), chemical vapordeposition (CVD) or sputtering.

[0028]FIG. 2 is a flow chart showing the steps for removing contaminantsfrom a silicon wafer after chemical-mechanical polishing according to afirst preferred embodiment of this invention.

[0029] As shown in FIG. 1C, a portion of the metallic layer 110 outsidethe opening 104 must be removed to form the damascene structure. Inother words, step S10 in FIG. 2 needs to be carried out. Achemical-mechanical polishing of the metallic layer 110 is conductedwhile using the barrier layer 108 as a polishing stop layer. Thepolishing process is stopped when the barrier layer 108 is exposed.

[0030] However, dishing of the metallic layer 110 may occur afterpolishing. Dishing is particularly intense if the metallic layer 110 isa copper layer. Hence, a portion of the dielectric layer 102 near theedges of the metallic layer 110 may be exposed and polished away.Consequently, the particulate dielectric material may form a layer ofcarbon-rich particles on the surface of metallic layer 110. Inparticular, if the dielectric layer 102 is a low dielectric constantmaterial layer, size and number of carbon-rich particles thus producedwill increase considerably. Since the carbon particles and the metallicsurface often have opposite polarity in most types of slurry, thecarbon-rich particles mostly attach to the surface of the copper layerleading, to the formation of surface defects.

[0031] Therefore, in step S12, the wafer is transferred to abuffer-polishing station and an aqueous solution of ozone is deliveredto the wafer. Utilizing the mechanical forces within thebuffer-polishing station, the ozone molecules within the aqueoussolution react with residual contaminants or carbon-rich particles onwafer surface. The reacted particles are subsequently carried away bythe solution. Concentration of ozone is the aqueous solution ispreferably between about 10 ppm and 200 ppm and mechanical forceprovided by the buffer-polishing station is preferably between about 0.5psi and 3 psi.

[0032] In addition, the step S12 can also be carried out inside achemical-mechanical polishing stationby passing an aqueous ozonesolution in between the polishing pad and the wafer. Utilizing theinertial mechanical force of the polishing pad, the ozone moleculeswithin the aqueous solution react with residual contaminants orcarbon-rich particles on wafer surface. The reacted particles aresubsequently carried away by the solution. Similarly, concentration ofozone is the aqueous solution is preferably between about 10 ppm and 200ppm and mechanical force provided by the polishing pad is preferablybetween about 0.5 psi and 3 psi.

[0033] The wafer is transferred back to the chemical-mechanicalpolishing station so that step S14 can be carried out. As shown in FIG.1D, chemical-mechanical polishing of the barrier layer 108 is conductedto form a complete damascene structure. However, dishing of the metalliclayer may still occur in during barrier-CMP. Hence, a considerableamount of carbon-rich particles derived from the broken pieces of thedielectric layer 102 may still cover the wafer surface after removingthe barrier layer 108, especially when the dielectric layer 102 is a lowdielectric constant material layer. Moreover, the carbon particles andthe metal surface are generally oppositely charged in the presence ofslurry. Therefore, the carbon-rich particles can easily attach to themetallic surface, leading to surface defects.

[0034] In step S16, the wafer is transferred to a buffer-polishingstation. An aqueous solution of ozone is delivered to thebuffer-polishing station. Utilizing the mechanical forces within thebuffer-polishing station, the ozone molecules within the aqueoussolution react with residual contaminants or carbon-rich particles onthe wafer surface. The reacted particles are subsequently carried awayby the solution. Concentration of ozone in the aqueous solution ispreferably between about 10 ppm and 200 ppm and mechanical forceprovided by the buffer-polishing station is preferably between about 0.5psi and 3 psi.

[0035] In addition, the step S16 can also be carried out inside achemical-mechanical polishing station by passing an aqueous ozonesolution in between the polishing pad and the wafer. Utilizing theinertial mechanical force of the polishing pad, the ozone moleculeswithin the aqueous solution react with residual contaminants orcarbon-rich particles on the wafer surface. The reacted particles aresubsequently carried away by the solution. Similarly, concentration ofozone is the aqueous solution is preferably between about 10 ppm and 200ppm and mechanical force provided by the polishing pad is preferablybetween about 0.5 psi and 3 psi.

[0036] Finally, in step S18, the wafer is brushed, jet-cleaned orultrasonic-cleaned inside a cleaner using conventional cleaning solutionor de-ionized water. Since the process used in step S18 is identical toa conventional wafer cleaning or post-CMP wafer treatment, detaileddescription is omitted.

[0037] Furthermore, the aqueous ozone solution is preferably catalyzedbefore conducting step S12 or S16. The catalysis increases the quantityof free radicals inside the solution and improves cleaning efficiency ofthe ozone solution. The ozone solution is catalyzed, for example, byshining ultraviolet light into the solution or putting hydrogen peroxidewith a concentration roughly 2 to 4 times that of ozone into thesolution.

[0038]FIG. 3 is a flow chart showing the steps for removing contaminantsfrom a silicon wafer after chemical-mechanical polishing according to asecond preferred embodiment of this invention.

[0039] As shown in FIG. 1C, a portion of the metallic layer 110 outsidethe opening 104 must be removed to form the damascene structure. Inother words, step S20 in FIG. 3 needs to be carried out. Achemical-mechanical polishing of the metallic layer 110 is conductedwhile using the barrier layer 108 as a polishing stop layer. Thepolishing process is stopped when the barrier layer 108 is exposed.

[0040] However, dishing of the metallic layer 110 may occur afterpolishing. Dishing is particularly intense if the metallic layer 110 isa copper layer. Hence, a portion of the dielectric layer 102 near theedges of the metallic layer 110 may be exposed and polished away.Consequently, the particulate dielectric material may form a layer ofcarbon-rich particles on the surface of metallic layer 110. Inparticular, if the dielectric layer 102 is a low dielectric constantmaterial layer, size and number of carbon-rich particles thus producedwill increase considerably. Since the carbon particles and the metallicsurface often have opposite polarity in most types of slurry, thecarbon-rich particles mostly attach to the surface of the copper layer,leading to the formation of surface defects.

[0041] In step S22, a chemical-mechanical polishing of the barrier layer108 is conducted to form a complete damascene structure as shown in FIG.1D. However, dishing of the metallic layer may still occur in thebarrier-CMP. Hence, a considerable amount of carbon-rich particlesderived from the broken pieces of the dielectric layer 102 may stillcover the wafer surface after removing the barrier layer 108, especiallywhen the dielectric layer 102 is a low dielectric constant materiallayer. Moreover, the carbon particles and the metal surface aregenerally oppositely charged in the presence of slurry. Therefore, thecarbon-rich particles can easily attach to the metallic surface leadingto surface defects.

[0042] In step S24, the wafer is transferred to a buffer-polishingstation. An aqueous solution of ozone is delivered to thebuffer-polishing station. Utilizing the mechanical forces within thebuffer-polishing station, the ozone molecules within the aqueoussolution react with residual contaminants or carbon-rich particles onthe wafer surface. The reacted particles are subsequently carried awayby the solution. Concentration of ozone is the aqueous solution ispreferably between about 10 ppm and 200 ppm and mechanical forceprovided by the buffer-polishing station is preferably between about 0.5psi and 3 psi.

[0043] In addition, the step S24 can also be carried out inside achemical-mechanical polishing station by raising the wafer to providesome space. An aqueous ozone solution is introduced between thepolishing pad and the wafer. Utilizing the inertial mechanical force ofthe polishing pad, the ozone molecules within the aqueous solution reactwith residual contaminants or carbon-rich particles on wafer surface.The reacted particles are subsequently carried away by the solution.Similarly, concentration of ozone is the aqueous solution is preferablybetween about 10 ppm and 200 ppm and mechanical force provided by thepolishing pad is preferably between about 0.5 psi and 3 psi.

[0044] Finally, in step S26, the wafer is brushed, jet-cleaned orultrasonic-cleaned inside a cleaner using conventional cleaning solutionor de-ionized water. Since the process used in step S26 is identical toa conventional wafer cleaning or post-CMP wafer treatment, detaileddescription is omitted.

[0045] Furthermore, the aqueous ozone solution is preferably catalyzedbefore conducting step S24. The catalysis increases the number of freeradicals inside the solution and improves cleaning efficiency of theozone solution. The ozone solution is catalyzed, for example, by shiningultraviolet light into the solution or putting hydrogen peroxide with aconcentration roughly 2 to 4 times that of ozone into the solution.

[0046]FIG. 4 is a flow chart showing the steps for removing contaminantsfrom a silicon wafer after chemical-mechanical polishing according to athird preferred embodiment of this invention.

[0047] As shown in FIG. 1C, a portion of the metallic layer 110 outsidethe opening 104 must be removed to form the damascene structure. Inother words, step S30 in FIG. 4 needs to be carried out. Achemical-mechanical polishing of the metallic layer 110 is conductedusing the barrier layer 108 as a polishing stop layer. The polishingprocess is stopped when the barrier layer 108 is exposed.

[0048] However, dishing of the metallic layer 110 may occur afterpolishing. Dishing is particularly intense if the metallic layer 110 isa copper layer. Hence, a portion of the dielectric layer 102 near theedges of the metallic layer 110 may be exposed and polished away.Consequently, the particulate dielectric material may form a layer ofcarbon-rich particles on the surface of metallic layer 110. Inparticular, if the dielectric layer 102 is a low dielectric constantmaterial layer, size and number of carbon-rich particles thus producedwill increase considerably. Since the carbon particles and the metallicsurface often have opposite polarity in most types of slurry, thecarbon-rich particles mostly attach to the surface of the copper layer,leading to the formation of surface defects.

[0049] In step S32, a chemical-mechanical polishing of the barrier layer108 is conducted to form a complete damascene structure as shown in FIG.1D. However, dishing of the metallic layer may still occur in thebarrier-CMP. Hence, a considerable amount of carbon-rich particlesderived from the broken pieces of the dielectric layer 102 may stillcover the wafer surface after removing the barrier layer 108, especiallywhen the dielectric layer 102 is a low dielectric constant materiallayer. Moreover, the carbon particles and the metal surface aregenerally oppositely charged in the presence of slurry. Therefore, thecarbon-rich particles can easily attach to the metallic surface leadingto surface defects.

[0050] Finally, in step S34, the wafer is transferred to a cleaningstation. Inside the cleaning station, an aqueous solution of ozone isdelivered to the wafer while the wafer is scrubbed, jet-cleaned orultrasonic-cleaned. Residual contaminants on the wafer surface reactwith ozone in the solution to form dislodged particles. The particlesare carried away by the solution. Concentration of ozone in the aqueoussolution is preferably between about 10 ppm and 200 ppm and mechanicalforce provided by the polishing pad is preferably between about 0.5 psiand 3 psi.

[0051] To be compatible with subsequent processing steps, otherchemicals may also be added to the aqueous cleaning solution so that thewafer surface is treated at the same time.

[0052] Furthermore, the aqueous ozone solution is preferably catalyzedbefore conducting step S34. The catalysis increases the number of freeradicals and improves cleaning efficiency of the ozone solution. Theozone solution is catalyzed, for example, by shining ultraviolet lightinto the solution or putting hydrogen peroxide with a concentrationroughly 2 to 4 times that of ozone into the solution.

[0053] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A method of removing contaminants from a siliconwafer after a chemical-mechanical polishing operation, comprising:performing a buffer-polishing process by passing an aqueous solution ofozone over the silicon wafer.
 2. The method of claim 1, wherein aconcentration of ozone in the aqueous solution is between about 10 ppmand 200 ppm.
 3. The method of claim 1, wherein performing abuffer-polishing process includes providing an inertial mechanical forceof between about 0.5 psi and 3 psi.
 4. The method of claim 1, whereinthe buffer-polishing process is conducted after a metallic layerchemical-mechanical polishing process.
 5. The method of claim 1, whereinthe buffer-polishing process is conducted after a barrier layerchemical-mechanical polishing process.
 6. The method of claim 1, whereinbefore performing the buffer-polishing process, the aqueous ozonesolution is catalyzed to produce more free ozone radicals therein. 7.The method of claim 6, wherein the aqueous ozone solution is catalyzedby exposure to a beam of ultraviolet light or addition of hydrogenperoxide thereto.
 8. A method of forming a dual damascene structure,comprising: providing a substrate; forming a dielectric layer over thesubstrate; patterning the dielectric layer to form an opening thatexposes a portion of the substrate; forming an etching stop layer overthe substrate, wherein the etching stop layer is conformal to a surfaceprofile of the substrate; removing the etching stop layer within theopening by photolithographic and etching techniques; forming a barrierlayer over the substrate, wherein the barrier layer is conformal to thesurface profile of the substrate and covers the etching stop layer;forming a metallic layer over the barrier layer so that the opening iscompletely filled; performing metallic layer chemical-mechanicalpolishing to remove a portion of the metallic layer and expose thebarrier layer; performing barrier layer chemical-mechanical polishing toremove a portion of the barrier layer and expose the dielectric layer;and performing a buffer-polishing process by passing thereover anaqueous solution of ozone so that contaminants on a surface of the waferare removed.
 9. The method of claim 8, wherein after metallic layerchemical-mechanical polishing but before barrier layerchemical-mechanical polishing, further includes: performing a secondbuffer-polishing process by passing an aqueous solution of ozone overthe silicon wafer.
 10. The method of claim 9, wherein a concentration ofozone in the aqueous solution is between about 10 ppm and 200 ppm andperforming the second buffer-polishing process includes providing aninertial mechanical force of between about 0.5 psi and 3 psi.
 11. Themethod of claim 9, wherein before performing the first buffer-polishingprocess or before performing the second buffer-polishing process furtherincludes catalyzing the aqueous ozone solution to produce more freeozone radicals in the solution.
 12. The method of claim 11, wherein theaqueous ozone solution is catalyzed by exposure to a beam of ultravioletlight or addition of hydrogen peroxide thereto.
 13. The method of claim8, wherein a concentration of ozone in the aqueous solution is betweenabout 10 ppm and 200 ppm and performing the first buffer-polishingprocess includes providing an inertial mechanical force of between about0.5 psi and 3 psi.
 14. The method of claim 8, wherein the dielectriclayer includes a low dielectric constant material layer and the metalliclayer includes a copper layer.
 15. A method of forming a dual damascenestructure, comprising: providing a substrate; forming a dielectric layerover the substrate; patterning the dielectric layer to form an openingthat exposes a portion of the substrate; forming an etching stop layerover the substrate, wherein the etching stop layer is conformal to asurface profile of the substrate; removing the etching stop layer withinthe opening by photolithographic and etching techniques; forming abarrier layer over the substrate, wherein the barrier layer is conformalto the surface profile of the substrate and covers the etching stoplayer; forming a metallic layer over the barrier layer so that theopening is completely filled; performing metallic layerchemical-mechanical polishing to remove a portion of the metallic layerand expose the barrier layer; performing barrier layerchemical-mechanical polishing to remove a portion of the barrier layerand expose the dielectric layer; and performing a water-cleaningoperation by passing an aqueous solution containing ozone over thesilicon wafer so that the substrate is surface-treated.
 16. The methodof claim 15, wherein a concentration of ozone in the aqueous solution isbetween about 10 ppm and 200 ppm.
 17. The method of claim 15, whereinthe water-cleaning step includes providing an inertial mechanical forceof between about 0.5 psi and 3 psi.
 18. The method of claim 15, whereinthe aqueous ozone solution is catalyzed before performing thewater-cleaning process to produce more free ozone radicals therein. 19.The method of claim 18, wherein the aqueous solution is catalyzed byexposure to a beam of ultraviolet light or addition of hydrogen peroxidethereto.
 20. The method of claim 15, wherein the dielectric layerincludes a low dielectric constant material layer and the metallic layerincludes a copper layer.